A close associate of Émile Durkheim who undertook studies of egalitarianism, democracy, socialism, a general study of social values (The Evolution of Values, 1922), and a review of sociology in Germany. His most important work was a study of the Indian caste system (Essays on the Caste System, 1908). In this study he showed that the mechanical solidarity (see division of labour) of the hierarchical caste system confines people within specific social groups and gives them only a very restricted freedom of action. This was a major influence on the later work of Louis Dumont (Homo Hierarchicus, 1966). He was a supporter of anarchism and edited the complete works of Pierre Proudhon, who he saw as proposing important sociological ideas.